1. Field of the Invention
The following invention relates generally to electrical solenoids and motors, and more specifically to reducing internal heating of electrical solenoids and motors during operation.
2. Related Art
Electromagnetic solenoids and motors produce internal heating during operation. This internal heating is due to electrical power dissipated in resistive heating of magnetic coils, as well as frictional losses, inside the device. This internal heating is detrimental to device performance in that it produces an increased operating temperature. Many materials used in the conductors, insulation, and other working parts of these devices are adversely affected by increased temperature. Therefore, maintaining low operating temperatures would simplify design, lower cost, and benefit device life and performance levels.
The performance and reliability of electrical solenoids and motors are diminished by increased internal temperatures caused by waste power dissipation. The internal temperature increase causes the electrical resistance of the electromagnet coil windings to increase for all practical conductor materials. Practical conductor materials include aluminum, copper, silver, gold, and other materials. Given a fixed device supply voltage, which is usually the case, the solenoid or motor windings carry less current as their resistance increases. This reduced current results in less electromagnetic force produced by the coils, and therefore useful work being generated by the device. In this way, solenoids and motors become less powerful as they heat up due to internal power dissipation leading to unmitigated temperature rise in the electromagnet windings.
Today, this operational performance limitation is normally compensated by over-sizing the motor or solenoid such that it provides excess force or power at the start-up condition, as well as the required force or power at the hot (thermally-degraded) operating conditions. Devices designed for steady-state operation must rise to a temperature at which the rate of heat rejection to the environment equals the rate of waste heat input. Devices designed for low duty cycle, or short-duration, operation also rely on a large internal thermal capacity of the device itself to limit the temperature rise to safe levels. What is required is a method, and system accompanying this method, for significantly reducing these deleterious effects of the internal heating of electromagnetic solenoids, motors, and similar devices, without resorting to over-sized devices, or devices that are excessively difficult and expensive to manufacture.